Ground flare

ABSTRACT

A ground flare for treating waste gas comprises a rectangular enclosure including opposing first and second side walls and opposing first and second end walls. The first and second side walls have a greater length than the first and second end walls. At least one air opening is formed in each of the first and second side walls for receiving air. At least one burner extends horizontally through each of the at least one air opening and into the enclosure. Each burner includes a fuel port disposed inside of the enclosure for injecting the waste gas into the enclosure.

FIELD OF THE INVENTION

This invention relates generally to chemical and industrial processes and systems. Particular applications of the invention include ground flares for refineries, petrochemical plants, and gas processing plants.

BACKGROUND OF THE INVENTION

In industrial systems, such as refineries, petrochemical plants, and gas processing plants, it is often necessary to remove waste gas from an industrial process for environmental or other reasons. One common way to remove waste gas is by combusting the waste gas in a ground flare. In a ground flare, waste gas is combined with introduced air and combusted (flared off) to remove undesirable chemicals. The treated waste gas is vented to atmosphere. Ground flares allow waste gas to be disposed of safely without the need to shut down a plant.

One type of ground flare is an enclosed ground flare, a particular example of which is a totally enclosed ground flare (TEGF). In a typical TEGF, an enclosure is provided having a plurality of vertically-fired burners disposed therein. The enclosure is typically formed by walls that are combined to form a square shape, with a refractory insulation lining formed on inner walls. The burners typically extend upwardly from a lower portion of the enclosure, which can be ground or an additional lower surface. Tips of the burners (flare tips) have a plurality of openings for waste gas to exit. Manifolds are provided in fluid communication with the burners for introducing the waste gas that exits through the burners. A pilot is provided for igniting the burners. The waste gas is combined with air that enters into the enclosure, and the waste gas is flared off.

TEGFs are favored for being environmentally friendly. However, TEGFs are quite large (e.g., on the order of thousands of square feet) and are typically of a standardized design. This design may not be optimal for a particular location, e.g., a particular plot at an industrial environment. Accordingly, to provide required waste gas treatment, multiple TEGF units are often used in industrial environments, which increases installation time and costs.

Therefore, there remains a need for a more effective and efficient apparatus for combusting waste gas in an industrial environment.

SUMMARY OF THE INVENTION

The present invention is directed to providing an effective and efficient apparatus and process for combusting waste gas.

Accordingly, in one aspect of the present invention, the present invention provides a ground flare for treating waste gas. The ground flare comprises a rectangular enclosure including opposing first and second side walls and opposing first and second end walls. The first and second side walls have a greater length than the first and second end walls. At least one air opening is formed in each of the first and second side walls for receiving air. At least one burner extends horizontally through each of the at least one air opening and into the enclosure. Each burner includes a fuel port disposed inside of the enclosure for injecting the waste gas into the enclosure.

In some embodiments, the enclosure extends upwardly from ground.

In some embodiments, the ground flare further comprises a rectangular wind fence surrounding the enclosure, wherein the enclosure is substantially centered within the wind fence.

In some embodiments, the enclosure comprises a lower portion and an upper portion.

In some embodiments, the at least one air opening comprises a plurality of air openings formed along the length of each of the first and second side walls. It is contemplated that the plurality of air openings on the first side wall are aligned with the plurality of air openings on the second side wall. It is further contemplated that the at least one burner comprises a plurality of burners coupled to a manifold disposed above the air opening. It is also contemplated that the at least one burner comprises a plurality of sets of burners, each set of burners being coupled to a manifold disposed above the air opening.

In some embodiments, the ground flare further comprises at least one air entrainment port formed into each of the first and second end walls for receiving air therethrough.

Another aspect of the present invention provides a ground flare for treating waste gas. The ground flare comprises a rectangular enclosure including opposing first and second side walls and opposing first and second end walls, wherein the first and second side walls have a greater length than the first and second end walls. Each of the first and second side walls comprises a plurality of segments, each segment including at least one air opening formed therein for receiving air. At least one burner extends horizontally through each of the at least one air opening and into the enclosure. Each burner includes a fuel port disposed inside of the enclosure for injecting the waste gas into the enclosure.

In some embodiments, each burner comprises a pipe that extends through the air opening, and a flare tip comprising a plurality of the fuel ports.

In some embodiments, the at least one burner comprises a plurality of burners. Each burner comprises a pipe that extends through the air opening and a flare tip comprising a plurality of the fuel ports.

In some embodiments, the ground flare further comprises a plurality of steam injection ports disposed in the enclosure.

In some embodiments, each of the segments is substantially identical.

In some embodiments, the air openings comprise windows formed into the first and second side walls.

In some embodiments, the ground flare further comprises further comprises at least one air entrainment port formed into each of the first and second end walls for receiving air therethrough.

In some embodiments, each of the first and second side walls and the first and second end walls comprises upper and lower sections.

Another aspect of the invention provides a ground flare for treating waste gas. The ground flare comprises a rectangular enclosure including opposing first and second non-firing walls and opposing first and second firing walls. The first and second firing walls comprise a plurality of repeating segments, each segment including at least one air opening formed therein for receiving air. A plurality of burners extend horizontally from outside the enclosure through each of the at least one air opening and into the enclosure. Each burner includes a fuel port disposed inside of the enclosure for injecting the waste gas into the enclosure.

In some embodiments, for each air opening, the plurality of burners are coupled to a manifold disposed above the air opening.

In some embodiments, the ground flare further comprises a wind fence disposed around the enclosure and surrounding the enclosure. The enclosure is centered within the wind fence.

In yet another aspect of the present invention, a ground flare includes at least two, at least three, or all of the above described aspects of the present invention.

Additional objects, embodiments, and details of the invention are set forth in the following detailed description of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a ground flare according to an embodiment of the invention;

FIG. 2 is a side elevation view of the ground flare of FIG. 1, in which a portion of a wind fence is transparent;

FIG. 3 is a top plan view of the ground flare of FIG. 1;

FIG. 4 is a side elevation view of the ground flare of FIG. 1;

FIGS. 5A and 5B are front elevation views of a flare tip with (FIG. 5A) and without (FIG. 5B) steam injection; and,

FIG. 6 is a perspective view of a portion of the ground flare of FIG. 1, with the wind fence and end walls removed for illustration.

DETAILED DESCRIPTION

Referring to FIGS. 1-4, a ground flare, generally designated 10, is shown for treatment of waste gas from an industrial environment, such as a refinery, a petrochemical plant, or a gas processing plant. The example ground flare 10 is a totally enclosed ground flare (TEGF). The ground flare 10 includes an enclosure 12, in which combustion of the waste gas takes place. The enclosure 12 is disposed on and extends upwardly from ground 14.

The enclosure 12 is formed of opposing first and second side walls 16, 18 and opposing first and second end walls 20, 22. It will be appreciated that “first” and “second” are used for convenience of illustration, and do not indicate a particular order. The walls 16, 18, 20, 22 each are made up of a lower wall portion 16 a, 18 a, 20 a, 22 a and an upper wall portion 16 b, 18 b, 20 b, 22 b. In the example enclosure 12, the lower wall portions 16 a, 18 a, 20 a, 22 a are formed together as a lower section, and the upper wall portions 16 b, 18 b, 20 b, 22 b are formed together as an upper section. The lower section and upper section can be assembled to provide the enclosure 12. The upper wall portions 16 b, 18 b, 20 b, 22 b provide a stack for the enclosure 12. One or more doors (not shown) can be provided on one or more of the lower wall portions 16 a, 18 a, 20 a, 22 a for allowing entry to the enclosure 12.

The first and second side walls 16, 18 and the first and second end walls 20, 22 are formed from a material suitable for withstanding the amount of heat generated in the enclosure 12 during combustion of the waste gas and reflecting the heat within the enclosure. The material can also be selected for particular desired heat transfer characteristics. Example materials for the walls 16, 18, 20, 22 include stainless steel and carbon steel. Inner walls of the first and second side walls 16, 18 and the first and second end walls 20, 22 can be lined with refractory insulation, as will be appreciated by those of ordinary skill in the art.

The first and second side walls 16, 18 provide firing walls for the ground flare 10, in that waste gas is flared near these walls. The first and second end walls 20, 22 preferably are non-firing walls. As best viewed in FIG. 3, each of the first and second side walls 16, 18 have a greater length than each of the first and second end walls 20, 22, so that the enclosure 12 is rectangular, i.e., it defines a rectangular area therein. The ratio between lengths of each of the first and second side walls 16, 18 and lengths of each of the first and second end walls 20, 22 (that is, the ratio of the lengths of the firing walls to the lengths of the non-firing walls, or the ratio of the enclosure's 12 length to its width) can be any ratio greater than 1:1. As described in more detail below, the length:width ratio of the enclosure 12 can be selectively increased or decreased by increasing or decreasing the length of the first and second side walls 16, 18, but this ratio should be greater than 1:1, so that the enclosure is rectangular.

A wind fence 26 surrounds the enclosure 12, and includes first and second side walls 28, 30 and first and second end walls 32, 34. As with the enclosure 12, the wind fence 26 is preferably rectangular in shape. Further, as best viewed in FIG. 3, the enclosure 12 preferably is generally centered within the (rectangular) area enclosed by the wind fence 26. The walls 28, 30, 32, 34 can be made of sheets of steel, preferably with an interior layer of refractory material for insulation. As shown in FIGS. 1, 2, 4, and 6, the height of the wind fence 26 is lower than a height of the enclosure 12, and preferably lower than a height of the lower wall portions 16 a, 18 a, 20 a, 22 a of the enclosure. The wind fence 26 protects units surrounding the ground flare 10 from exposure to radiation, and protects combustion taking place within the ground flare from wind disturbance.

Referring to FIGS. 1 and 4, in some example embodiments, the first and second end walls 20, 22, which are preferably the non-firing walls, have air entrainment ports 40, such as windows, formed therein and providing air entrainment for the ground flare 10 (only the ports on end wall 20 are viewable in FIGS. 1 and 4). The size and number of the air entrainment ports 40 can be selected based on air requirements for the enclosure 12. In some example embodiments, the air entrainment ports 40 on both end walls 20, 22 are equally sized and aligned in facing relationship with one another across the length of the enclosure 12. The air entrainment ports 40 provide additional airflow to the waste gas during combustion to help reduce or minimize a required plot space for combusting a desired amount of waste gas. The air entrainment ports 40 also keep the non-firing walls (e.g., end walls 20, 22) cool by keeping flame off of the non-firing walls. In other example embodiments, the air entrainment ports 40 are omitted.

As best viewed in FIGS. 1-3 and 6, the first and second side walls 16, 18, and preferably the lower portions 16 a, 18 a, include a plurality of evenly spaced air openings, such as windows 50 formed into the first and second side walls. The windows 50 are open to atmosphere for entry of air therethrough. A plurality of burners 52 extend horizontally through the windows 50, in a direction generally normal to each of the first and second side walls 16, 18 (FIGS. 4, 6), and towards the longitudinal center of the enclosure 12. Preferably, the windows 50 and burners 52 are arranged generally symmetrically along the enclosure 12, and the windows 50 preferably are sized equally for providing equal amounts of air through each window. Among other benefits, arranging and sizing the windows 50 in this way allows for a more uniform air distribution. The upper portions 16 b, 18 b of the side walls 16, 18 preferably are solid, though it is contemplated that additional windows and burners could be provided.

Each burner 52 includes a horizontally extending pipe 54 having an inner end terminating in a flare tip 56 “Inner” refers to an end that is closer to an interior of the enclosure 12. The pipes 54 are preferably cylindrical. An example material for the pipes 54 and the flare tip 56 is stainless steel. FIG. 5A shows an example flare tip 56, which includes one or more (as shown, eight, though this number could be higher or lower) linearly extending fuel ports 58, disposed symmetrically around a center 60 that is coupled to an inner end of the pipe 54. A plurality of openings 62, e.g., throughholes, are formed in a surface of each of the fuel ports 58 for dispersing waste gas fed to the pipes 54. In an example embodiment, and as shown by example in FIG. 5A, the openings 62 are disposed in similar or identical locations along each fuel port 58. The flare tip 56 preferably is slightly angled (e.g., 5°-25°, and preferably about 15°) upward and to the right with respect to the (horizontal) longitudinal axis of the pipe 54 (e.g., facing toward the center of the enclosure 12 from outside). This improves flame behavior during waste gas combustion.

In some embodiments, multiple burners 52 extend through each window 50. For instance, in the example ground flare 10, each window 50 has extending therethrough a plurality of (as shown, three) sets 70 a, 70 b, 70 c of burners 52, forming an array. Each set 70 a, 70 b, 70 c includes a plurality of (as shown, three) burners 52, each having an outer end (“outer” referring to being away from the interior of the enclosure) of their respective pipe 54 connected to a vertically extending pipe 72. As shown in FIGS. 1-4, and 6, this array of burners 52 can be generally oriented along a plane that is substantially parallel to the first and second side walls 16, 18. This allows one to increase the number of burners 52 and thus outlets for dispersing waste gas without encroaching further into the interior of the enclosure 12, which can otherwise weaken the access to air in the middle of the enclosure.

The pipes 72 are connected to an upper manifold 74, which in turn is coupled to a gas runner 76 (e.g., a pipe) for introduction of compressed waste gas from an industrial environment. The gas runner 76 can be coupled to one or more valves (not shown) for selective delivery of waste gas to the ground flare 10. The upper manifold 74, the gas runner 76, and valves, which are heat-sensitive components, preferably are disposed above the window 50 so that they can be more easily shielded from radiation due to flame during waste gas combustion.

As best viewed in FIG. 6, the vertical positions of the burners 52 along each pipe 72 are preferably staggered between sets 70 a, 70 b, and 70 c, so that a larger overall area is defined by the multiple (as shown, nine) burners. It will be appreciated that the configurations for the horizontal burners, including the configuration of the manifold, flare tips, gas runner, etc., as well as the number and arrangement of the burners horizontally extending through the windows, can vary from those shown and described herein.

Referring to FIGS. 1 and 5B, in some example embodiments, selected windows (e.g., windows 78 in FIG. 1) on the first and second side walls 16, 18 are provided with a steam injection apparatus 80 to shorten the flame during waste gas combustion. In the example ground flare 10 shown in FIG. 1, windows 78 are indicated to illustrate windows in which the steam injection apparatus is implemented, though it will be appreciated that any of the other windows, in any combination, could be used. As best viewed in FIG. 5B, the example steam injection apparatus 80 includes a plurality of preferably linearly extending steam injection ports 82 that are disposed behind the flare tips 56, which can be between the flare tips and the inner surface of the first side wall 16 or the second side wall 18. Preferably, each of the steam injection ports 82 are symmetrically disposed about the center 60 of the flare tip 56, near respective ones of the linear fuel ports 58 so that each of the steam injection ports is adjacent to each of the fuel ports, respectively. To supply steam, the steam injection ports 82 each are coupled via a fluid coupling 84 to a steam supply line 85 and have openings 86, e.g., throughholes, for dispensing steam. The steam supply line 85 can be configured to surround the pipes 54, so that the steam supply line extends horizontally with the pipes. The steam supply line 85 can be coupled to a steam supply (not shown). Preferably, the steam injection ports 82 are made from stainless steel.

In an example operation of the ground flare 10, compressed waste gas is supplied to the flare tips 56 in each set 70 a, 70 b, 70 c of the burners 52 by the gas runners 76. Steam can also be supplied through the steam injection ports 82. Air enters through the windows 50 on the firing walls; i.e., first and second side walls 16, 18 having the burners 52 extending therethrough, and (in some embodiments) air enters through the air entrainment ports 40 on the non-firing walls (first and second end walls 20, 22). A pilot (not shown) fires continuously to ignite the waste gas exiting the flare tips 56, and the waste gas is combusted within the enclosure 12. The treated waste gas after combustion (flue gas) can exit through the top of the enclosure 12.

Referring to FIG. 6, the enclosure 12 can be considered to be made up of a plurality of modular segments 90. Each modular segment 90 can include, for instance, a portion of each of the first and second side walls 16, 18 that includes one or more pairs (one, two, three, or more pairs) of opposed windows 50, each having a set 70 a, 70 b, 70 c of burners 52. As one non-limiting example, as shown in FIG. 6, a portion of the first and second side walls 16, 18 surrounding one pair of opposed windows 50 can be considered a modular segment 90. As another example, a larger portion of the first and second side walls 16, 18 surrounding two pairs of opposed windows can be considered a modular segment, and the first or second window in each pair can be provided with the steam injection apparatus 80. In another example, the portions of the first and second side walls 16, 18 surrounding the three opposed pairs of windows 50 in FIG. 6 can be considered a single modular segment. The modular segments 90 can be substantially identical, in that the windows 50 can be disposed at the same location along the segment, and the burners 52 in the windows can be disposed in the same location within the window. However, this is not required in all embodiments. Repeating modular segments 90 can be provided as needed to meet various waste gas combustion requirements to form the first and second side walls and, in turn, the enclosure 12.

By “segments,” it is not required that the modular segments 90 be formed separately and assembled. Multiple modular segments 90 can be embodied in separately-formed portions, or segments can be integrally formed as a single unit. A combination is also possible, e.g., some modular segments can be integrally formed, while additional segments are connected. Providing or adding more modular segments 90 increases the length of the enclosure 12, and thus increases the length:width ratio of the rectangular enclosure.

This example modular configuration for the enclosure 12 provides a flexible design for enclosure length, and corresponding heat release. The enclosure 12 size and length:width ratio can be customized, limited only by available plot size. Using this example modular configuration, a single ground flare 10 can be provided with an enclosure 12 length that is selected (e.g., by selecting the number of modular segments 90) to reduce the required number of units. By forming the enclosure 12 from repeating segments 90, a symmetrical, rectangular enclosure can be provided, which in turn provides a more uniform air distribution and combustion within the enclosure. Further, using horizontally-fired burners in example ground flares allows an increased diameter for burners while still providing access to air in the middle of the units.

The rectangular shape of the enclosure 12 allows for a larger amount heat release in a smaller area versus a square-shaped or circular enclosure. This results in a greater heat density. The horizontally fired burners 52 allow heat-sensitive components (such as the manifolds, the gas runners, and the valves) to be more easily shielded from radiation due to flame. Further, as opposed to burners with round combustors, which can lower the access to air in an enclosure as the diameter increases, example burners 52 and arrangements allow multiple burners without lowering air access. By providing windows 50 that are substantially equal in size and location, and substantially equal arrangements for the burners 52 within each window, equal amounts of air can be made available for each window, resulting in a more uniform air distribution. The upper portions 16 b, 18 b of the side walls, and thus the overall enclosure 12, can be made shorter due to a sterile zone that can occur at the bottom of the ground flare, e.g., between the lower portions 16 a, 18 a of the side walls. Further, the example modular design of the ground flare 10 allows for a customized length and heat release that can be made as large as needed.

Though the size of the ground flare can vary as needed or desired, a larger ground flare can increase the cost per flow rate of waste gas that is flared off. Further, providing the ground flare 10 as a single unit maximizes the use of available plot space for a particular environment (e.g., a refinery, petrochemical plant, gas processing plant, etc.). A single unit, enclosed ground flare can also be more environmentally friendly.

A ground flare including at least one of the above aspects is beneficial and desirable for the reasons described herein.

It should be appreciated and understood by those of ordinary skill in the art that various other components such as valves, pumps, filters, coolers, etc. were not shown in the drawings as it is believed that the specifics of same are well within the knowledge of those of ordinary skill in the art and a description of same is not necessary for practicing or understating the embodiments of the present invention.

While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims and their legal equivalents. 

What is claimed is:
 1. A ground flare for treating waste gas, the ground flare comprising: a rectangular enclosure including opposing first and second side walls and opposing first and second end walls, wherein the first and second side walls have a greater length than the first and second end walls; at least one air opening formed in each of the first and second side walls for receiving air; and at least one burner extending horizontally through each of the at least one air opening and into the enclosure, each burner including a fuel port disposed inside of the enclosure for injecting the waste gas into the enclosure.
 2. The ground flare of claim 1, wherein the enclosure extends upwardly from ground.
 3. The ground flare of claim 1, further comprising: a rectangular wind fence surrounding said enclosure, wherein said enclosure is substantially centered within the wind fence.
 4. The ground flare of claim 1, wherein the enclosure comprises a lower portion and an upper portion.
 5. The ground flare of claim 1, said at least one air opening comprises a plurality of air openings formed along the length of each of the first and second side walls.
 6. The ground flare of claim 5, wherein the plurality of air openings on the first side wall are aligned with the plurality of air openings on the second side wall.
 7. The ground flare of claim 5, wherein said at least one burner comprises a plurality of burners coupled to a manifold disposed above said air opening.
 8. The ground flare of claim 5, wherein said at least one burner comprises a plurality of sets of burners, each set of burners being coupled to a manifold disposed above said air opening.
 9. The ground flare of claim 1, further comprising: at least one air entrainment port formed into each of the first and second end walls for receiving air therethrough.
 10. A ground flare for treating waste gas, the ground flare comprising: a rectangular enclosure including opposing first and second side walls and opposing first and second end walls, wherein the first and second side walls have a greater length than the first and second end walls; each of the first and second side walls comprising a plurality of segments, each segment including at least one air opening formed therein for receiving air; and at least one burner extending horizontally through each of the at least one air opening and into the enclosure, each burner including a fuel port disposed inside of the enclosure for injecting the waste gas into the enclosure.
 11. The ground flare of claim 10, wherein each burner comprises: a pipe that extends through the air opening; and a flare tip comprising a plurality of the fuel ports.
 12. The ground flare of claim 10, wherein said at least one burner comprises a plurality of burners, each burner comprising: a pipe that extends through the air opening; and a flare tip comprising a plurality of the fuel ports.
 13. The ground flare of claim 11, further comprising: a plurality of steam injection ports disposed in the enclosure.
 14. The ground flare of claim 10, wherein each of the segments is substantially identical.
 15. The ground flare of claim 10, wherein the air openings comprise windows formed into the first and second side walls.
 16. The ground flare of claim 10, further comprising: at least one air entrainment port formed into each of the first and second end walls for receiving air therethrough.
 17. The ground flare of claim 10, wherein each of the first and second side walls and the first and second end walls comprises upper and lower sections.
 18. A ground flare for treating waste gas, the ground flare comprising: a rectangular enclosure including opposing first and second non-firing walls and opposing first and second firing walls, the first and second firing walls comprising a plurality of repeating segments, each segment including at least one air opening formed therein for receiving air; and a plurality of burners extending horizontally from outside the enclosure through each of the at least one air opening and into the enclosure, each burner including a fuel port disposed inside of the enclosure for injecting the waste gas into the enclosure.
 19. The ground flare of claim 18, wherein, for each air opening, the plurality of burners are coupled to a manifold disposed above the air opening.
 20. The ground flare of claim 18, further comprising: a wind fence disposed around the enclosure and surrounding the enclosure; wherein the enclosure is centered within the wind fence. 